Variable valve mechanisms according to Patent Documents 1 to 5 are all configured as follows. That is, as in a variable valve mechanism 80 according to a first related art (Patent Document 1) illustrated in FIG. 10, for example, the variable valve mechanisms include a rocker arm 82 that drives a valve 7. The rocker arm 82 includes a roller arm 83 including a roller 83a that rotatably abuts against a cam 81, and a side arm 84 provided at a side of the roller arm 83.
The variable valve mechanisms further include switching pins 86 and 86 and a hydraulic chamber 87 provided inside the rocker arm 82. The variable valve mechanisms switch the drive state of the valve 7 by displacing the switching pins 86 between a coupling position at which the switching pins 86 extend between the roller arm 83 and the side arm 84 and a non-coupling position at which the switching pins 86 do not extend between the roller arm 83 and the side arm 84 based on variations in hydraulic pressure in the hydraulic chamber 87.